Marine propeller with resilient hub structure

ABSTRACT

A MARINE PROPELLER AND HUB STRUCTURE FOR ABSORBING SUDDEN ROTATIONAL LOADS WHICH MAY BE APPLIED TO THE PROPELLER WHEN ITS STRIKES A SUBMERGED OBJECT. THE HUB STRUCTURE FOR THE PROPELLER INCLUDES AN INNER HUB, A PLURALITY OF RIBS EXTENDING RADIALLY OUTWARDLY FROM THE INNER HUB AND AN OUTER HUB JOINED TO THE INNER HUB BY THE RADIALLY EXTENDING RIBS. THE PROPELLER ASSEMBLY IS COMPLETED BY A PLURALITY OF BLADES EXTENDING OUTWARDLY FROM THE OUTER HUB. THE RIBS OF THE HUB STRUCTURE ARE FLEXIBLE ENOUGH TO PROVIDE A RESILIENT CUSHIONING EFFECT IN THE PROPELLER HUB STRUCTURE WHEN A BLADE STRIKES AN UNDERWATER OBSTACLE.

Oct. 31, 1972 E. LAMBRECHT 3,701,511

MARINE PROPELLER WITH RESILIENT HUB STRUCTURE Filed Dec. 21, 1970 w HG.

INVENTOR RALPH E. LAMBRECHT ATTOR EY United rates Patent O 3,701,611MARINE PROPELLER WITH RESILIENT HUB STRUCTURE Ralph E. Lambrecht, LakeBluff, Ill., assignor to Outboard Marine Corporation, Waukegan, Ill.Filed Dec. 21, 1970, Ser. No. 99,882 Int. Cl. B6311 21/26 US. Cl.416-134 6 Claims ABSTRACT OF THE DISCLOSURE A marine propeller and hubstructure for absorbing sudden rotational loads which may be applied tothe propeller when it strikes a submerged object. The hub structurefor'the propeller includes an inner hub, a plurality of ribs extendingradially outwardly from the inner hub and an outer hub joined to theinner hub by the radially extending ribs. The propeller assembly iscompleted by a plurality of blades extending outwardly from the outerhub. The ribs of the hub structure are flexible enough to provide aresilient cushioning eifect in the propeller hub structure when a bladestrikes an underwater obstacle.

BACKGROUND OF THE INVENTION When a marine propeller strikes anunderwater obstacle it often causes extensive damage to the propelleritself or to the propeller driving mechanism. In the past, resilientdrive connections between various parts in the propeller assembly suchas slip clutch mechanisms have been provided to absorb these suddentorque forces transmitted through the propeller when it strikes such anobstacle. In order to absorb the excessive torque forces throughslippage, the previous drive assemblies and connections have beenexpensive to manufacture and complicated in structure. This invention isa simple, economical propeller that provides a resilient cushioningeffect in one integral part of the propeller rather than between variousconnecting parts in the propeller.

SUMMARY OF THE INVENTION The invention relates to a marine propelleradapted to operate immersed in Water and more particularly to animproved marine propeller having a hub structure that is resilient toexcessive torque loads.

A primary object of this invention is a marine propeller for absorbingexcessive torque loads thereby reducing the damage to the blades and/orpossible damage to the mechanism driving the propeller.

A further object is a propeller and hub structure that provides aresilient cushioning eifect in the hub structure when the propellerstrikes an underwater object.

Another object is an improved marine propeller that may be fabricated inone piece from one of the memory plastics.

Another object is a propeller that is simple in structure and economicalto manufacture.

Other objects and advantages will be apparent from the followingdescription and accompanying drawings for this invention.

The drawings:

FIG. 1 is a partial axial section view through the hub structure of amarine propeller in accordance with the invention.

FIG. 2 is a section view taken along lines 22 of FIG. 1.

FIG. 3 is a section view of another embodiment of this invention showingdeflection of the radially extending ribs when they are under excessivetorque loads.

DETAILED DESCRIPTION Referring to the drawings in more detail it will beseen that the marine propeller 10 includes a hub structure 12 and aplurality of blades 24 extending radially outwardly from the hubstructure to provide the driving force to propel a watercraft (notshown). The hub structure 12 may be adapted to be mounted on a sleevearound a propeller shaft 14 such as the bushing 16 shown in FIGS. 1 and2. The hub structure may also be adapted to be mounted directly on thepropeller shaft 14 as shown in FIG. 3.

The hub structure 12 includes a means for providing a resilientcushioning effect when the propeller 10 hits a submerged object. The hubstructure 12 is comprised of an inner hub 18, a plurality of ribs 20extending radially outwardly from the inner hub, and an outer hub 22joined to the inner hub by the radially extending ribs. The hubstructure and particularly the ribs .20 are adapted to provide a meansfor deflection in the propeller 10 when it is subject to excessivetorque loads.

FIG. 1 is a partial section view showing in detail the propeller 10 andparticularly the hub structure 12. The propeller shaft 14 is tranverselybored to receive a shear pin 28 in a conventional manner. The bushing 16is mounted on the propeller shaft 14 for common rotary movement with theshaft. The inner hub as shown at 18 is mounted around the bushing 16.The inner hub 18 is posi tively connected to the bushing by any numberof locking means such as the use of pins, splines, or knurls. FIG. 1shows the outer surface of the bushing 16 as having knurls which areadapted to interconnect with complementary knurls on the inner surfaceof the inner hub 18. The shear pin 18 passes through the bushing 16 topositively drive both the bushing and the inner hub from the propellershaft 14 while the shear pin remains intact.

In accordance with the invention, the outer hub 22 forms part of the hubstructure 12. As shown the outer hub 22 is located in radially outwardlyspaced relationship to the inner hub 18. The outer hub 22'is connectedto the inner hub by the plurality of radially extending ribs .20. Aplurality of blades 24 extend outwardly from the outer hub 22 in aconventional manner. It is important to note that the ribs 20 must berigid enough to withstand the normal rotational forces transmitted tothe hub structure by the rotating propeller blades 20 but flex-i ibleenough to deflect when the blades strike a submerged object.

As shown in FIG. 1, the inner hub 18, ribs 20, outer hub 22 and blades24 may all be fabricated as one integral piece. The fabrication of thehub structure 12 and blades 24 as one integral piece may be accomplishedby injection molding the propeller assemblyfrom any one of the commonlyknown memory plastics.

FIG. 2 is a section view taken along lines 2-2 of FIG. 1, showing an endview of the propeller 10 and the hub structure 12 for this invention. Itwill be noted that the propeller 10 is shown as having two blades 24.The propeller of thi invention is adapted for use with a marinepropulsion unit of any horsepower however, it is probably best adaptedfor an outboard motor having a relatively low horsepower output.

FIG. 2 clearly shows the disposition and shape of the ribs 20 forconnecting the inner hub 18 to the outer hub 22. The plurality of ribs20 are radially disposed in relationship to the propeller shaft 14. Theribs 20 each have an inner end 30 and an outer end 32 with a mid-section34 therebetween. The mid-section 34 is thicker in cross section than theends providing a larger cross sectional area for added strength to keepthe hub structure 12 from collapsing under various loading conditions.The disposition and shape of the ribs 20 is important as it allows thepropeller to deflect under excessive loads thereby allowing thepropeller to withstand shock and torque loads without any permanentdeformation to the propeller.

The resilient cushion effect provided by the hub structure 12 when itstrikes an under water obstacle substantially reduces the amount ofblade damage and substantially eliminates damage to the expensivemechanism driving the propeller. Among other advantages this provides asafety feature as loss of a propeller blade or the driving mechanism canresult in a propellent that will not function effectively and thus leadto a disabled craft.

FIG. 3 shows another embodiment of the hub structure 12 for thisinvention. In this embodiment an inner hub 18 is splined directly to thepropeller shaft 14 for common rotary movement with the shaft. Thesplines 36 of the inner hub fit into key-ways formed by complimentarysplines 38 on the propeller shaft 14.

A plurality of radially extending ribs 20 join the inner hub 18 to anouter hub 22. The outer hub 22 is adapted to carry the usual propellerblades (not shown). In this embodiment the ribs 20 are shown underdeflection as would occur if a blade of the propeller struck anunderwater obstacle.

It should be noted that the hub structure 12 and the blades 24 may befabricated as two separate parts. For example, the hub structure 12shown in FIG. 3 may be extruded as a separate piece from one of thememory plastics. The blade 24 may be fabricated separately and attachedto the outer hub 22 in any conventional manner.

All or a part of the propeller 10 can be made from one of the commonlyknown memory plastics. More specifically, the ribs 20 alone or the hubstructure 12 alone or the hub structure and blades 24 can be made fromone of the commonly known memory plastics. The plastic resin utilizedshould have high impact strength and dimensional stability. In addition,it should be substantially non-water absorbent. Polyethylene andpolypropylene are two plastic resins which have been found to work well.

It is important to note that the plurality of ribs 20 must be able toabsorb the stress of operation without flexing while providing aresilient cushioning effect in the hub structure 12 when the propellerhits an underwater object. Therefore, .the material used for the ribs 20must be able to withstand repeated flexing without cracking.

In addition, it is important to note that the propeller for thisinvention may be used with an exhaust system that discharges exhaustthrough a snout when using a cap 25 as shown in FIG. 1 or it can beeffectively used with a through the hub propeller exhaust system.

Various features of the invention are set forth in the following claims.

What is claimed is:

1. A hub structure for a marine propeller, said hub structure beingconstructed in one piece from one of the memory plastics and includingan inner hub adapted to be mounted on a propeller shaft for commonrotary movement with the propeller shaft, means for providinga'resilient cushioning effect when the propeller hits a submerged objectincluding a plurality of ribs extending radially outwardly from saidinner hub, and an outer hub joined to said inner hub by said radiallyextending ribs and located in radially outwardly spaced relationship tosaid inner hub.

2. A hub structure in accordance with claim 1 wherein each said rib hasan inner end connected to said inner hub, an outer end connected to saidouter hub, and a mid-section therebetween of larger cross sectional areathan either of said ends.

3. A hub structure in accordance with claim 1 wherein said inner hubincludes interlocking splines connected to the propeller shaft toprovide positive driving engagement between the propeller shaft and saidinner hub.

4. A hub structure in accordance with claim 1 further including aplurality of blades extending integrally and outwardly from said outerhub.

5. A propeller assembly for use with a marine propulsion unit fordriving a watercraft, said propeller assembly including a propellershaft, a bushing mounted on said propeller shaft for common rotarymovement with said shaft, and a unitary member fabricated in one piecefrom one of the memory plastics including an inner hub mounted aroundsaid bushing in positive driving engagement with said bushing, means forproviding a resilient cushioning effect in the propeller assembly whenthe propeller hits a submerged object including a plurality of ribsextending radially outwardly from said inner hub, an outer hub joined tosaid inner hub by said radially extending ribs and located in radiallyoutwardly spaced relationship to said inner hub, and a plurality ofblades extending outwardly from said outer hub to provide a thrust forceto drive the watercraft.

6. A propeller assembly in accordance with claim 5 wherein each said ribhas an inner end connected to said inner hub, an outer end connected tosaid outer hub, and a mid-section therebet-ween of larger crosssectional area than either of said ends.

References Cited UNITED STATES PATENTS 2,235,605 3/1941 Bugatti 416l342,543,396 2/1951 Wolff 6427 R X 3,012,767 12/1961 Jones 6427 R X3,133,596 5/1964 Berliner 416-24 A X 3,245,476 4/1966 Rodwick 4l6241 A3,318,388 5/1967 Bihlmire 416-240 X 3,477,794 11/1969 Abbott et al416l34 3,563,670 2/1971 Knuth 41693 M 3,584,969 6/1971 Aiki 416132EVERETTE A. POWELL, JR., Primary Examiner US. Cl. X.R.

